Experiments with a double solenoid system: Measurements of the 6 He+p - - PowerPoint PPT Presentation
Introduction Setup Analysis Summary Experiments with a double solenoid system: Measurements of the 6 He+p Resonant Scattering Rub en Pampa Condori Institute of Physics - USP 2015 53. International Winter Meeting on Nuclear Physics 26-30
Introduction Setup Analysis Summary
Rub´ en Pampa Condori
Institute of Physics - USP
2015
26-30 January 2015, Bormio, Italy
Introduction Setup Analysis Summary
Level scheme of 7He and 7Li1
region just above the threshold
system 6He+p.
p(6He, p)6He elastic scattering can provide information about the structure of the compound nucleus 7Li
11.24MeV 3/2− T=3/2 of the 7Li which is the IAS of the ground state of 7He
1D.R. Tilley et al., Nucl. Phys. A 745, 155(2002)
Introduction Setup Analysis Summary
S˜ ao Paulo Pelletron Laboratory
Introduction Setup Analysis Summary
RIBRAS system
beam by the primary reaction
9Be(7Li,6He).
polyethylene(CH2) in the mid-scattering chamber.
used a thick target of polyethylene(CH2) with thickness of 12mg/cm2.
Radioactive Ion Beams in Brasil (RIBRAS)
Introduction Setup Analysis Summary
RIBRAS system The primary beam comes from the left side and the secondary particles are produced in the primary target by nuclear reactions. The standard primary target is a 9Be foil of 8-12µm thickness. The primary beam is suppressed by a Faraday cup, connected to a current integrator module which provides the total incident charge.
Introduction Setup Analysis Summary
RIBRAS system
The first solenoid makes a Bρ =
√ 2mE q2
selection of the particles produced in the primary target. Particles with the same Bρ are focused in the ISO-250 intermediate scattering chamber and, unwanted particles are stopped by the collimators and blockers strategically positioned over the beam line.
Introduction Setup Analysis Summary
RIBRAS system Using a polyethylene foil as absorber in the mid-scattering chamber we improve the beam purity from 16% in the mid-scattering chamber to 92% in the secondary scattering chamber.
Introduction Setup Analysis Summary
Two detectors were mounted in the scattering chamber.
Introduction Setup Analysis Summary
Thick Target Method Thick Target Method
consists of using thick sheets of polyethylene CH2 to stop the secondary beam.
any position in the 6He range and the energy of the recoil protons is related to the energy
scattering position.
Introduction Setup Analysis Summary
Thick Target Method Thick Target Method
may happen in any point x of the CH2 target and the recoil protons have to travel a distance
L−x cosθlab .
loss energy in the distance
L−x cosθlab , so this is
loss of energy is calculated and added to the energy of the detected protons.
To calculate this loss of energy we used the programs STOPX and KINEQ.
Introduction Setup Analysis Summary
Spectrum measured with a CH2(12mg/cm2) target at E
6He lab
= 12.2MeV
We also conduct measurements with a pure carbon target intended to measure the effect which could cause the carbon present in the polyethylene target(CH2). As we can see in carbon target there is no line in the area corresponding to the proton.
Introduction Setup Analysis Summary
Spectra measured with a CH2(12mg/cm2) target at E
6He
lab = 12.2MeV
In this figure we can see the proton line projection into energy-axis. The contribution of the carbon is shown by the dashed curve in this spectrum. As we can see no peaks are seen in the region around the resonance peak in the carbon spectrum.
Introduction Setup Analysis Summary
The energy resolution of 1MeV(FWHM) and intensity of 1000pps. ∆Ep = ∆E6He dx dE
dE dx
We know that: dE dx ∝ MZ 2 E so: ∆Ep = ∆E6He E6He m6HeZ 2
6He
mpZ 2
p
Ep ∼ 90KeV (1)
Introduction Setup Analysis Summary
dΩ
The experimental differential cross section dσ/dΩ is given by: dσ
dΩ
NcontJ ∆ΩNtargetNbeam
Where Ntarget is the number of scatterer nuclei inside the target per unit area Nbeam is the total number of incident particles of the beam that hit the target and ∆E6He is the 6He energy step Ntarget =
∆E6He
dE6He dx
Introduction Setup Analysis Summary
dE/dx(MeV/mg*cm )
Energia He(MeV)
There was made a polynomial fit to these points ( dE
dx ) obtained
with the STOPX code.
Introduction Setup Analysis Summary
Spectra measured with a CH2(12mg/cm2) target at E
6He lab
= 11.5 − 12MeV and Excitation Functions E∗
7Li = Ecm + Qp+6He fus
Introduction Setup Analysis Summary
Breit-Wigner function2
The spectra have been fitted by a Breit-Wigner function (2) folded with a gaussian whose width is the experimental resolution σexp.res.
c.m.
= 90keV(3). L(E) = NΓ(E, ℓ) (E − Er )2 + Γ(E,ℓ)2
4
(2) Lc (E) = Z dE′L(E′) e
−(E−E′)2 2σ2 res
√ 2πσres (3) θlab N = γ2
p
Γ(keV ) Er (MeV ) 0◦ 0.052 ± 0.004 254 ± 24 11.11 ± 0.02 20◦ 0.011 ± 0.001 262 ± 25 11.28 ± 0.02 25◦ 0.036 ± 0.001 256 ± 27 11.11 ± 0.03
2The fit was performed using the program XFIT developed by Guilherme Amadio
(http://www.cecm.usp.br/∼amadio/aboutme)
Introduction Setup Analysis Summary
R-matrix calculations-Excitation Functions E ∗
7Li = Ecm + Qp+6He
fus
We have also performed R-matrix calculation considering two decays channels: (p,p) and (p,n) The latter measured by Rogachev et al. Γp Γ ≈ 0.2 and Γn Γ ≈ 0.8
n γ2 p
= 2 Γ = Γp + Γn = 0.265MeV = 2γ2
r Pℓ(ER ) + 2γ2 nPℓ(ER − Q) =
0.265MeV
3Calculations have been performed by P.Descouvemont.
Introduction Setup Analysis Summary
R-matrix calculations-Excitation Functions E ∗
7Li = Ecm + Qp+6He
fus
Introduction Setup Analysis Summary
R-matrix calculations-Excitation Functions E ∗
7Li = Ecm + Qp+6He
fus
Introduction Setup Analysis Summary
R-matrix calculations-Excitation Functions E ∗
7Li = Ecm + Qp+6He
fus
Introduction Setup Analysis Summary
The multi-channel algebraic scattering (MCAS) method solves the coupled-channel Lippmann- Schwinger LS equations describing a two-cluster system, in both bound-state sub-thresholds and scattering regimes.
4Calculations have been performed by L. Canton.
Introduction Setup Analysis Summary
function at three angles θproton
lab
=0, 20 and 25 degrees. We clearly see peaks in the position corresponding to the 11.24MeV, state of the 7Li.
shows that the peak has the expected energy and width at the three angles.
with the data. Reasonable results are obtained for the (p,p)
used the partial widths reported in Rogachev et al. for the (p,p) and (p,n) channel.
Introduction Setup Analysis Summary
We will work with three telescopes at θlab = 0, 25, 45 degrees(which correponding to θcm = 180, 130, 90 degrees) to
be sure that the three angles correspond to the same Nbeam and we will have an angular distribution. This was not the case in the previous experiment when the measurement a 25degrees was taken with a different run.
Introduction Setup Analysis Summary
ao Paulo - IFUSP
epine-Szily, R. Lichtenth¨ aler, V. Guimaraes, L. Gasques, P. N. de Faria, K.C.C. Pires, V. Scarduelli, M.C. Morais, R. Pampa Condori, E. Leistenschneider, E. Benjamim, O. Camargo Jr. J.Alcantara-Nunez,
P.R.S. Gomes, J. Lubian, J.M.B. Shorto, D.S. Monteiro, D. R. Mendes, V. Morcelle
e Libre de Bruxelles, Brussels, Belgium
A.M. Moro, M. Rodr´ ıguez-Gallardo
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Finnancial Support: